The field of the present invention relates to fixed optical reading systems, for example bar code scanning systems, which include multiple windows through which optical reading may be accomplished.
Fixed barcode scanners having multiple windows capable of reading objects in a variety of orientations have been on the market for some time. One such "multi-plane" scanner is described in U.S. Pat. No. 5,475,207 entitled "Multiple Plane Scanning System for Data Reading Applications", which is hereby incorporated by reference. These multi-plane or "multi-window" scanners are high performance scanners which use one or more scanned optical beams to generate multiple scan patterns. Mechanically, these scanners have one or more scan engines and multiple scan windows oriented in different planes from each other, instead of a single scan window as in single-plane scanners. One of the scan windows is usually oriented horizontally, defining a horizontal scan plane, while the other window or windows are oriented to have significant vertical components and define additional substantially vertical scan plane(s). The additional vertical scan plane(s) enable the scanner to successfully read a barcode from a larger fraction of the surface of the object for a given object orientation.
Horizontal window barcode scanning systems which also include a weigh scale apparatus have also been available for several years. One such "scanner scale" weighing apparatus is described in U.S. Pat. No. 5,410,108, which is hereby incorporated by reference. The weighing apparatus may take the form of a load cell which bears a rigid framework referred to hereinafter as a "spider". The spider supports a weigh platter onto which objects are placed to be weighed.
Alternately, the apparatus may be a "spiderless" scale in which the weigh platter is sufficiently rigid in itself to obviate the need for a spider. The weigh platter may comprise a horizontal flat piece of rigid material such as metal or a combination of metal amd plastic with an optically transparent portion corresponding to a horizontal scan window. The transparent portion allows transmission of optical beams out from a scan engine and transmission of optical barcode signals back into the scanner. The load cell, which is well-known in the art, usually comprises a machined piece of aluminum with one or more strain gauges attached thereto. When an object is placed on the weigh platter, the mechanical stress thus applied to the load cell generates electrical signals from the strain gauges, and these signals are in turn used to determine the weight of the object. When incorporated as part of an optical barcode scanning system, the load cell, spider, and weigh platter may preferably comprise a separate sub-assembly from the optical scanner.
In one device such as the 1994 version of the Spectra-Physics MAGELLAN.TM. scanner/scale, the load cell and spider are positioned below the scan engine, and vertical support members are connected to the spider, extend upward around the scanner, and are connected to the weigh platter, which is positioned over the scan engine.
Fixed optical barcode scanners with multiple scan planes have been combined with a weighing apparatus such as the Spectra-Physics MAGELLAN.TM. scanner/scale. The MAGELLAN.TM. scanner scale is a dual plane scanner having a vertical scan plane and a horizontal scan plane with a horizontal weigh platter.
Multiple plane scanners such as the MAGELLAN.TM. unit, however, may encounter several problems when a weigh scale is being incorporated. The addition of a second scan plane adds to the size of the scan unit. Since these systems are often used in locations where space is a significant limitation, such as a supermarket checkout stand, the addition of a second scan plane often comes at the expense of decreased area of the horizontal weigh platter. This decrease in area increases the likelihood that the vertical scan components, vertical scan window, and their associated housing will interfere mechanically with an object placed on the weigh platter to be weighed. Moreover, the limited size of the weigh platter may result in an object being weighed (depending upon its size) to extend past the edge of the platter onto the counter potentially resulting in an inaccurate weight measure.
In addition, horizontal single plane scanners with weigh platters typically have an air gap which completely surrounds the platter, allowing dust, dirt, and debris to fall around the scanner (but not on the horizontal scan window) so as not to interfere with scanner function. Moreover, the weigh platter may simply extend beyond the horizontal extent of the horizontal plane scanner.
In a dual plane scanner, since there can be no air gap or weigh platter extension on the side of the weigh platter adjacent the vertical scan window, debris may accumulate under the weigh platter which in turn may obstruct the horizontal scan window or may inhibit proper scale operation.